linux-kernel - Re: [PATCH net-next] net: phy: qca807x: move interface mode check to .config_init

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Date: Tue, 13 Feb 2024 14:27:32 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Robert Marko <robimarko@...il.com>, andersson@...nel.org,
	konrad.dybcio@...aro.org, hkallweit1@...il.com,
	linux@...linux.org.uk, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, linux-arm-msm@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: phy: qca807x: move interface mode check to
 .config_init_once

> > Yes, that is correct and when SFP is plugged in it will be reconfigured
> > by the driver into combo mode as that port can actually be used for fiber and
> > copper at the same time by changing the priority.
> >
> 
> Hi Andrew, just to make sure this doesn't get confused.
> 
> There is a HW limitation here and it's described in Documentation:
> 
> - In QSGMII mode the SFP Cage can't be connected or mounted physically
>   as in this mode only 5 copper port can be connected, it would go
>   against the HW design of the chip. In this configuration the first 4
>   port are qsgmii and the 5th port is sgmii. (we enforce qsgmii on all
>   ports out of simplicity to make sure we have a sane configuration in
>   DT)
> 
> - In PSGMII mode the 5th port is always a combo port that can either be
>   a copper port or a fiber port (with SFP cage). To set the 5th port to
>   fiber mode, the mode has to be switched but the other 4 port are
>   always copper.
>   Also it's ok to set the initial PSGMII mode to 5 copper port as it
>   will be changed as soon as a SFP cage is connected. (can't happen to
>   have a device with both a copper port and a SFP cage connected to the
>   5th port, it's one or the other. Again it would go against the HW
>   design.
> 
> Hope it's clear now why the check was introduced and the HW limitation
> of it as with the previous message one might think the 5th port is
> totally separated and can go to his own mode (PSGMII or QSGMII)

Thanks for the explanation

I'm more used to it being like:

&eth2 {
        /* ethernet@...00 */
        bm,pool-long = <3>;
        bm,pool-short = <1>;
        buffer-manager = <&bm>;
        managed = "in-band-status";
        phys = <&comphy5 1>;
        phy-mode = "sgmii";
        sfp = <&sfp0>;
        status = "okay";
};

Here phy-mode is set to one of the modes the SFP will use, either
sgmii or 1000baseX. But i don't think it matters what value is used.

      Andrew